The effect of activation versus inhibition of feedback on perceived control of EEG activity

This study explores a model in which perceived control is affected by multiple sources of feedback at three different stages of the control sequence — person, response, and outcome. Behavior that enhances feedback is termedactivation, while behavior that diminishes feedback is termedinhibition. The study tests the hypothesis that activation at any stage of the sequence leads to greater perceived control than inhibition. Eighty subjects increased or decreased their brain-wave activity (EEG) by making a tone go either on or off, using either an active or a passive strategy. Following 10 60-second trials, subjects rated their perception of control over their EEG activity. The hypothesis that making a tone go on (activation of the outcome) leads to a greater perception of control than making the tone go off (inhibition of the outcome) was confirmed only when subjects decreased their EEG activity. Perceived control was not significantly correlated with actual control, supporting the expectation that they are separately mediated. The results did not support the hypothesis that increasing EEG activity or using an activity strategy would lead to a greater perception of control than decreasing EEG or using a passive strategy. These findings are interpreted as evidence that attention to feedback may be necessary for the predicted bias in perceived control to occur, and that activation and inhibition should be operationalized as the absolute presence versus absence of feedback in testing the hypothesis for the first two stages of control.This article is based on a dissertation submitted to Yale University in partial fulfillment of the requirements for the doctoral degree.     

Efficacy of EEG biofeedback procedures in correcting stress-related functional disorders

A promising approach to nondrug correction of human stress-induced functional disorders based on double EEG biofeedback (EEGBF) has been substantiated and experimentally tested. According to this approach, narrow-band EEG oscillators that are characteristic of each patient and detectable in real-time are simultaneously used in two independent feedback loops: the traditional adaptive biofeedback loop and an additional resonance stimulation loop. In the latter loop, the feedback signals from individual narrow-band EEG oscillators serve for automatic modulation of the parameters of sensory stimuli and are not perceived consciously by the subject. The combined use of the active (conscious perception) and passive (automatic modulation) feedback signals from narrow-band EEG components of the patient have been demonstrated to offer the possibility of a substantial increase in the efficacy of EEGBF.     

Perceived exertion is associated with an altered brain activity during exercise with progressive hyperthermia.

The present study tested the hypothesis that perceived exertion during prolonged exercise in hot environments is associated with changes in cerebral electrical activity rather than changes in the electromyogram (EMG) of the exercising muscles. Therefore, electroencephalogram (EEG) in three positions (frontal, central, and occipital cortex), EMG, rating of perceived exertion (RPE), and core temperature were measured in 14 subjects during submaximal exercise in normal (18 degrees C, control) and hot (40 degrees C, hyperthermia) environments. RPE increased from 11 +/- 1 units at 5 min to 20 +/- 0 units at exhaustion (50 +/- 3 min) in the trial with progressive hyperthermia, whereas exercise in the control trial was maintained with a stable core temperature for 1 h without exhausting the subjects. Altered EEG activity was observed in all electrode positions, and stepwise forward-regression analysis identified core temperature and a frequency index of the EEG over the frontal cortex as the best predictors of RPE. In contrast, there were no significant correlations between RPE and any of the measured EMG parameters (median spectral frequency, root mean square, or amplitude), and the EMG parameters were not different in hyperthermia compared with control. Thus hyperthermia does not seem to affect the activation pattern of the muscles. Rather, the linear correlation among core temperature, EEG frequency index, and RPE indicates that alterations in cerebral activity may be associated with the hyperthermia-induced development of fatigue during prolonged exercise in hot environments.     

Maintenance and generalization of 40-Hz EEG biofeedback effects

Maintenance of conditioning of 40-Hz EEG activity was investigated in six adults 1 to 3 years after they had experienced biofeedback training to increase 40-Hz EEG. Subjects were first retrained to alternately increase and suppress 40-Hz EEG. All six subjects achieved a preset performance criterion in 16–20 minutes. Five of these subjects also subsequently demonstrated significant control of 40-Hz EEG without feedback. The sixth subject did not demonstrate control after 76 minutes and four sessions of attempted retraining with feedback. Transfer of 40-Hz EEG control to a problem-solving task was tested in all subjects in a final session. Cognitive test items were presented and subjects were instructed to alternately increase and suppress 40-Hz EEG while solving the problems. Rates of 40-Hz EEG in suppression periods during problem solving were significantly greater than during suppression periods without problems. No significant differences in problem-solving performance were found comparing 40-Hz increase and suppression periods. This study supports previous research suggesting an association between 40-Hz EEG and mental activity, and suggests methods for further study of transfer of EEG biofeedback effects.     

Method of double feedback from EEG oscillators of the patient for correction of stress-induced functional disorders

Method of correction of human stress-induced functional disorders is proposed which is based on two feedback contours from narrow-band EEG oscillators of the patient. The first one is a usual biofeedback contour in which the feedback signals from the narrow-band EEG oscillator are consciously perceived by the patient and serve him as a guide for voluntary reduction/activation of these EEG components. The second one is an additional contour of resonance stimulation which helps a subject to overcome the difficulties of conscious control of feedback signals. In this contour the parameters of audio-visual stimulation are automatically tuned to the frequency of the dominant narrow-band EEG oscillator of the patient (from the same or other EEG frequency range) to reach its resonance activation. Scientific basis of the method is provided, the results of its experimental testing are presented.     

Kinematic and EMG characteristics of simple shoulder movements with proprioception and visual feedback.

The objective of this study was to determine if simple, shoulder movements use the dual control hypothesis strategy, previously demonstrated with elbow movements, and to see if this strategy also applies in the absence of visual feedback. Twenty subjects were seated with their right arm abducted to 90 degrees and externally rotated in the scapular plane. Subjects internally rotated to a target position using a custom shoulder wheel at three different speeds with and without visual feedback. Kinematics were collected with a motion analysis system and electromyographic (EMG) recordings of the pectoralis major (PECT), infraspinatus (INFRA), anterior and posterior (ADELT, PDELT) deltoid muscles were used to evaluate muscle activity patterns during movements. Kinematics changed as movement speed increased with less accuracy (p<0.01). Greater EMG activity was observed in the PECT, PDELT, and INFRA with shorter durations for the ADELT, PDELT and INFRA. Movements with only kinesthetic feedback were less accurate (p<0.01) and performed faster (p<0.01) than movements with visual feedback. EMG activity suggests no major difference in CNS control strategies in movements with and without visual feedback. Greater resolution with visual feedback enables the implementation of a dual control strategy, allowing greater movement velocity while maintaining accuracy.     

Multivariate EEG spectral analysis evidences the functional link between motor and visual cortex during integrative sensorimotor tasks

The identification of the networks connecting brain areas and the understanding of their role in executing complex tasks is a crucial issue in cognitive neuroscience. In this study, specific visuomotor tasks were devised to reveal the functional network underlying the cooperation process between visual and motor regions. Electroencephalography (EEG) data were recorded from twelve healthy subjects during a combined visuomotor task, which integrated precise grip motor commands with sensory visual feedback (VM). This condition was compared with control tasks involving pure motor action (M), pure visual perception (V) and visuomotor performance without feedback (V + M). Multivariate parametric cross-spectral analysis was applied to ten EEG derivations in each subject to assess changes in the oscillatory activity of the involved cortical regions and quantify their coupling. Spectral decomposition was applied to precisely and objectively determine the power associated with each oscillatory component of the spectrum, while surrogate data analysis was performed to assess the statistical significance of estimated coherence values. A significant decrease of the alpha and/or beta power in EEG spectra with respect to rest values was assumed as indicative of specific cortical area activation during task execution. Indeed alpha band coherence increased in proximity of task-involved areas, while it was suppressed or remained unchanged in other regions, suggesting the activation of a specific network for each task. According to our coherence analysis, a direct link between visual and motor areas was activated during V + M and VM tasks. The effect of visual feedback was evident in the beta band, where the increase of coherence was observed only during the VM task. Multivariate analysis suggested the presence of a functional link between motor and visual cortex subserving sensorimotor integration. Furthermore, network activation was related to the sum of single task (M and V) local effects in the alpha band, and to the presence of visual feedback in the beta band.     

Topographic EEG mapping of the relaxation response

The purpose of this study was to assess the central nervous system effects of the relaxation response (RR) in novice subjects using a controlled, within-subjects design and topographic EEG mapping as the dependent measure. Twenty subjects listened to a RR and control audiotape presented in a counterbalanced order while EEG was recorded from 14 scalp locations. TheRR condition produced greater (p<.0164) reductions in frontal EEG beta activity relative to the control condition. No significant differences were observed for any other frequency band or scalp region. These findings suggest that elicitation of the RR produces significant reductions in cortical activation in anterior brain regions in novice subjects.     

Serious-mindedness and the effect of self-induced respiratory changes upon parietal EEG

The role of serious-mindedness (so-called telic dominance) in regulation of parietal cortex EEG was investigated. Ten telic (serious-minded) and 10 paratelic (playful state-dominant) individuals were selected on the basis of their responses to the Telic Dominance Scale. They all performed instructed breathholding (hypopnea) and excessive breathing (hyperpnea) in counterbalanced order. The paratelic individuals yielded relatively high scores of integral EEG power; theta power was markedly increased in the left hemisphere during hyperpnea, and reduced in the right hemisphere during hypopnea. Both hyperpnea and hypopnea were reported to be more aversive to the paratelic than to the telic subjects, but no group difference in respiratory activity was found. The electrocortical and hedonic tone differences between the groups are discussed in relation to the distinction between the prefrontal (dopamine) activation pathway and frontoparietal (noradrenalin) arousal pathway, as well as in relation to changes in cortical blood flow and proprioceptive feedback.     

Hyperactive individuals as young adults: current and longitudinal electroencephalographic evaluation and its relation to outcome.

In a 10-year follow-up study electroencephalograms (EEGs) of 31 hyperactive and 27 matched control subjects of mean ages 19.17 and 18.59 years respectively showed no significant differences in any of the features assessed. Sequential EEGs, available for only the hyperactive subjects, suggested that a much greater proportion were normal at the 10-year follow-up assessment than at the 5-year follow-up assessment and that the normalization tended to take place mainly in the second 5-year period. This supports the hypothesis that EEG abnormalities of hyperactive persons are those of an immature pattern that tends to normalize with age. Correlation between EEG findings at the 10-year follow-up assessment and global outcome measures was not significant. Initial and 5-year EEGs also failed to predict global outcome at the 10-year follow-up assessment.     

Biofeedback in optimizing psychomotor reactivity: II. The dynamics of segmental α-activity characteristics

To estimate the EEG predictors of successful training in the voluntary control of psychomotor reactivity, 29 healthy young (aged 22.3 ± 1.5 years) musical performers were examined. The estimation was carried out in terms of segmental α-activity analysis using a biofeedback session as an example, simultaneously stimulating the EEG α rhythm and decreasing the muscle tone. On the first day of the study, the musicians followed instructions for the voluntary control of comfortable finger motor activity when performing musical passages for the right hand during a standard performance practice (without any use of an adaptive feedback). On the second day, the muscle tone and the power of the EEG α rhythm were voluntarily controlled in the context of a biofeedback technology. The analysis of the unsteady EEG segmentation showed that the dynamics of changes in the coherence and segmental characteristics of the α activity were the same for both effective biofeedback training and the standard successful performance practice: an increase in the α-rhythm coherence, an increase in the lifetime of α spindles, and a decrease in their amplitude variability. The results obtained are discussed in terms of the formation and dissociation of neuron ensembles in central mechanisms of optimal psychomotor functioning.     

The electrodermal indices of the subjective perception of performance errors during drowsy changes in consciousness

The study was aimed at searching for objective criteria of subject's perception of errors in performance due to drowsiness and estimating the time between the onset of errors and the moment of their awareness. Healthy subjects (n = 64) with the pronounced EEG alpha were examined under conditions without sleep deprivation. Experiments (n = 280) lasted for 40 min. During the experiments, the EEG, EOG, EDR, EKG, and button pressings were recorded and subject's reports were registered. The subjects were waken up after the onset of errors or 20 min after the beginning of the performance independently of errors. The error onset was shown to be preceded by the EEG "drowsy pattern" and decrease in the rate of spontaneous EDR. The performance reappearance after the error was accomplished by alpha-rhythm independently from error awareness. The interrogation of subjects after the error and activity revival demonstrated a correlation between the error subjective perception and appearance of the EDR. The interval between the error and the first following EDR (mean 10.1 s) was significantly (p < 0.001, t-test for dependent samples) shorter than the interval between the error and the last preceding EDR (mean 69.8 s). It is suggested that the subjective perception of an error is a significant endogenous stimulus, which evokes the orienting response and accompanying sympathetic activation.     

Behavioral and electroencephalographic correlates of 40-Hz EEG biofeedback training in humans

Two groups of eight adults successfully trained with biofeedback for increases in 40-Hz EEG responses in left or right hemispheres also demonstrated significant 40-Hz EEG increases during baseline periods, and increases in the contralateral hemisphere during training periods. No changes in heart rate, 40-Hz EMG, or 21- to 31-Hz beta, alpha, or theta EEG occurred over training days. Three subjects returning for additional training demonstrated suppression of 40-Hz EEG. A group of four subjects experiencing daily bidirectional training produced substantial within-session control of 40-Hz EEG but no changes over days. Data from posttraining tests without feedback for successful subjects in both groups indicated significant control of 40-Hz EEG responses in the initial parts of these sessions, and some correlated changes in other EEG responses. Measures of successful subjects' experiences during training and control tests indicated awareness of changes in subjective concomitants of EEG responses. This study suggests further strategies for research on behavioral correlates of EEG activity.     

Multi-Variate EEG Analysis as a Novel Tool to Examine Brain Responses to Naturalistic Music Stimuli

Note onsets in music are acoustic landmarks providing auditory cues that underlie the perception of more complex phenomena such as beat, rhythm, and meter. For naturalistic ongoing sounds a detailed view on the neural representation of onset structure is hard to obtain, since, typically, stimulus-related EEG signatures are derived by averaging a high number of identical stimulus presentations. Here, we propose a novel multivariate regression-based method extracting onset-related brain responses from the ongoing EEG. We analyse EEG recordings of nine subjects who passively listened to stimuli from various sound categories encompassing simple tone sequences, full-length romantic piano pieces and natural (non-music) soundscapes. The regression approach reduces the 61-channel EEG to one time course optimally reflecting note onsets. The neural signatures derived by this procedure indeed resemble canonical onset-related ERPs, such as the N1-P2 complex. This EEG projection was then utilized to determine the Cortico-Acoustic Correlation (CACor), a measure of synchronization between EEG signal and stimulus. We demonstrate that a significant CACor (i) can be detected in an individual listener''s EEG of a single presentation of a full-length complex naturalistic music stimulus, and (ii) it co-varies with the stimuli’s average magnitudes of sharpness, spectral centroid, and rhythmic complexity. In particular, the subset of stimuli eliciting a strong CACor also produces strongly coordinated tension ratings obtained from an independent listener group in a separate behavioral experiment. Thus musical features that lead to a marked physiological reflection of tone onsets also contribute to perceived tension in music.     

Desynchronization and synchronization of EEG related to stimuli triggering or forbidding sensory-motor reaction in adolescents: II. The peculiarities in case of the attention deficit and hyperactivity syndrome

Evoked desynchronization and synchronization of EEG in θ (4–7.5 Hz), α (7.5–14 Hz) and β (14–20 Hz) ranges were recorded by 19 electrodes in healthy volunteer adolescents and those with attention deficit hyperactivity syndrome in the modified GO/NO-GO test. Two stimuli (high and low tone) were presented in pairs with 1 s intervals inside the pair and 1.5 s intervals between the pairs. Test subjects had to push the button in response to presentation of a pair of high tones and to ignore other stimulus combinations. The components of evoked EEG synchronization in α-θ range that were revealed in the frontocentral and temporoparietal brain regions in connection with inhibition of action (inhibition of movements and making a decision to cancel sensory-motor task performance) were statistically significantly lower in subjects with attention deficit hyperactivity disorder compared with that in healthy subjects.     

EEG coherence during unconscious visual set under conditions of increased motivation of subjects

Prestimulus EEG was recorded in the state of "operative rest" after the instruction and at the stages of formation, actualization, and extinction of unconscious visual set to perception of unequal circles. Two motivation conditions were used: (1) subjects were promised to be rewarded with a small money price for each correct response (a "general" rise of motivation) and (2) only correct assessments of stimuli of a certain kind were rewarded (a "selective" rise of motivation). In both conditions, additional motivation of subjects to the results of their performance led to an increase in EEG coherence most pronounced in the theta and alpha 1 frequency ranges in the left temporal area of the cortex. During the "general" rise of motivation the EEG coherence (as compared to the control group) was higher in a greater number of derivation pairs than during the "selective" rise. EEG coherence in "motivated" subjects was increased already at the stage of operative rest. Later on, at the set stages, no significant changes were revealed. Thus, the realized set formed by the verbal instruction, which increased motivation of subjects to the results of their performance, produced substantially more prominent changes in coherence of cortical potentials than the unconscious set formed during perception of visual stimuli.     

Biofeedback of alveolar carbon dioxide tension and levels of arousal

This is a preliminary study designed to investigate the potential usefulness of alveolar (lung) CO2 feedback training in promoting sleep onset in primary insomniacs. The present study was undertaken to determine if normal subjects could, without obvious manipulation of breathing, bring alveolar (lung) CO2 tension under voluntary control using biofeedback techniques and, if so, whether this control would be accompanied by shifts in level of wakefulness. Subjects participated in five baseline and five training sessions in which EEG, alveolar CO2 tension, and thoracic/abdominal respiratory movement were monitored. The feedback consisted of a pitch-modulated tone plus visual scores. We found that CO2 tension in awake portions of "up" trials was significantly higher than for awake portions of "down" trials (p less than .01), indicating that learning had occurred. In the initial trials, when subjects raised CO2 tension they became drowsy and often fell asleep, and when they lowered CO2 tension they aroused themselves. However, when subjects were awakened immediately upon falling asleep, there developed a decoupling of EEG and CO2 changes. The presence of such a decoupling phenomenon makes it unclear whether CO2 feedback will be useful in promoting sleep onset in primary insomniacs.     

The Sensorium: Psychophysiological Evaluation of Responses to a Multimodal Neurofeedback Environment

The Sensorium is a multimodal neurofeedback environment that reflects a person’s physiological state by presenting physiological signals via orchestral sounds from a speaker and multi-coloured lights projected onto a white surface. The software manages acquisition, real-time processing, storage, and sonification of various physiological signals such as the electroencephalogram (EEG) or electrocardiogram (ECG). Each of the 36 participants completed 6 interventional conditions consisting of three different Sensorium-phases with EEG and ECG feedback, a mindfulness meditation, a guided body scan exercise, and a Pseudo-Sensorium using pre-recorded data that did not reflect the subject’s own physiology. During all phases EEG, ECG, skin conductance, and respiration were recorded. A feedback questionnaire assessed the participants’ subjective reports of changes in well-being, perception, and life-spirit. The results indicate that the Sensorium sessions were not statistically inferior compared to their corresponding active control conditions with respect to improvements in subjective reports concerning well-being and perception. Additionally, the Sensorium was rated as being a more extraordinary experience, as compared to meditation. During the Sensorium conditions the EEG showed lower levels of theta2 (7–8.5 Hz), alpha (9–12 Hz) and beta (12.5–25 Hz) activity. Since participants reported benefit from the Sensorium experience regardless of any prior experience with meditation, we propose this novel method of meditative and extraordinary self-experience to be utilized as a modern alternative to more traditional forms of meditation.